This invention relates generally to seat adjusters and more particularly it relates to an adjustable hinge mount for seats having reclinable backrest, such as motor vehicle seats, wherein a fixed hinge mount member is attached to the seat proper and a tiltable hinge mount member is attached to the backrest, the two hinge mount members being coupled one to another by means of a wobble gear having one of its gears supported for rotation on an eccentric sleeve which in turn is rotatable on a pivot axle projecting from one of the hinge mount members and the other gear of the wobble gear assembly is connected to the other hinge mount member.
In a known adjustable hinge mount of this type the pivot axle has the form of a hollow cylinder to accommodate in its interior a hand operated thrust bolt which in axial direction is rigidly connected to the eccentric sleeve to be axially displaced against the force of a resetting spring acting in the arresting direction. The eccentric sleeve has several sections eccentrically arranged relative to the pivot axle whereby one of the sections in the case of arresting the wobble gear enters an eccentric bore in that hinge mount member which is connected to the spur gear of the wobble gear assembly. Upon shifting axially the first bolt in the releasing direction the eccentric section is withdrawn from the eccentric bore in the aforementioned hinge mount member and as a result the spur gear formed on the hinge mount member which is connected to the backrest is permitted to roll in mesh with the inner gear of the fixed hinge mount member as soon as a force is applied in one or the other rotational direction on the backrest. when the eccentric sleeve is withdrawn from the bore of the spur gear, the circumference of another eccentric section of the sleeve rests on a flanged bearing formed on the spur gear and having an eccentric bore relative to the pivot axle. At the same time, the concentric bore of the eccentric sleeve is supported for rotation on the pivot axle by means of a roller bearing. In this manner it is ensured that the eccentric sleeve upon its withdrawal from the bore of the spur gear performs a synchronous wobbling movement relative to the spur gear which holds in mesh with the inner gear of the wobble gear assembly. In this manner, the front eccentric section of the eccentric sleeve which is rigidly connected to the thrust bolt can always in the axially released position of the latter locate the eccentric bore of the spur gear in order to establish a new locking connection between the spur gear and the inner gear of the wobble gear assembly. Accordingly, to enable an readjustment of the backrest, the thrust bolt and thus the eccentric sleeve have to be displaced in axial direction against the force of a resetting spring whereby in addition to the spring there act also the frictional forces between the eccentric section of the sleeve and the bore in the spur gear and also the resisting forces acting during the insertion of the eccentric sleeve into the flanged bearing and into the bearing of the pivot shaft. The magnitude of the force applied by the user of the seat in horizontal direction, nonetheless, is limited inasmuch as the seat user cannot apply his own weight for exerting a force acting in the horizontal direction. For these reasons, the operation of such known adjustable hinge mounts for a speedy adjustment of backrests is not always easy to be performed by any user of the seat.